In recent years, much research has been carried on in the area of diode lasers. Among the advantages of diode lasers are their small size, potentially low cost, low power requirements and capability of being modulated at very high data rates. In addition, diode lasers are extremely rugged devices since they do not use a glass gas discharge tube or external mirrors subject to misalignment. Furthermore, the power to light conversion efficiency of diode lasers is the highest of any laser operating at room temperature.
To meet the requirements for usage in a variety of applications, diode lasers must be provided which have device characteristics such as: very low output beam divergence, lowest order transverse mode operation at high pumping current levels, high peak pulsed output power, high differential quantum efficiency, and relative freedom from facet degradation usually resulting from high power densities.